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THE PERIPHERAL NERVOUS SYSTEM

THE PERIPHERAL NERVOUS SYSTEM. D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM. ORGANIZATION OF THE NERVOUS SYSTEM. BRAIN SPINAL CORD. CENTRAL NERVOUS SYSTEM (CNS). AFFERENT NERVES. EFFERENT NERVES. PERIPHERAL NERVOUS SYSTEM. EXTERO- RECEPTORS. INTERO-

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THE PERIPHERAL NERVOUS SYSTEM

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  1. THE PERIPHERAL NERVOUS SYSTEM D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM

  2. ORGANIZATION OF THE NERVOUS SYSTEM BRAIN SPINAL CORD CENTRAL NERVOUS SYSTEM (CNS) AFFERENT NERVES EFFERENT NERVES PERIPHERAL NERVOUS SYSTEM EXTERO- RECEPTORS INTERO- RECEPTORS SOMATIC AUTONOMIC EFFECTOR ORGANS SKELETAL MUSCLES SMOOTH AND CARDIAC MUSCLES AND GLANDS

  3. SENSORY INFORMATION TRAVELS TO THE BRAIN VIA SPECIALIZED PATHWAYS NEOCORTEX LIMBIC CORTEX NOSE SMELL THALAMUS EYE VISION TASTE TONGUE BRAIN STEM EAR AUDITION SKIN SOMATIC SPINAL CORD

  4. SENSORY MODALITIES AND RECEPTOR CELLS

  5. GRADED VS ALL OR NONE • A RECEPTOR’S RESPONSE TO A STIMULUS IS GRADED • IF THRESHOLD IS EXCEEDED, THE ACTION POTENTIAL RESULTING IS ALL OR NONE

  6. SENSORY MODALITIES AND RECEPTOR CELLS

  7. SENSORY TRANSDUCTION ADEQUATE STIMULUS MEMBRANE CONDUCTANCE CHANGE GENERATOR POTENTIAL ACTION POTENTIAL

  8. LOCALIZATION, DISTRIBUTION, AND ACUITY • CODING OF LOCATION DEPENDS ON RECEPTOR LOCATION • AREA COVERED BY RECEPTORS IN A SENSORY UNIT IS A RECEPTIVE FIELD • ACUITY DEPENDS ON THE DENSITY OF RECEPTORS

  9. SLOW PAIN • OCCURS AFTER A SECOND OR MORE • OFTEN ASSOCIATED WITH TISSUE DESTRUCTION • SUBJECTIVELY DESCRIBED AS BURNING, ACHING,THROBBING, NAUSEOUS, OR CHRONIC • C FIBERS WHICH SYNAPSE IN THE SUBSTANTIA GELITANOSA • FINAL PROJECTION IS THE FRONTAL CORTEX

  10. MECHANICAL, CHEMICAL AND THERMAL PAIN • FAST PAIN IS GENERALLY MECHANICAL OR THERMAL • SLOW PAIN CAN BE ALL THREE • CHEMICAL PAIN RECEPTORS: BRADYKININ, SEROTONIN, HISTAMINE, POTASSIUM IONS, ACIDS, ACETYL CHOLINE AND PROTEOLYTIC ENZYMES • PROSTAGLANDINS ENHANCE PAIN SENSATION

  11. BRAIN STRUCTURES AND PAIN • COMPLETE REMOVAL OF THE SENSORY CORTEX DOES NOT DESTROY THE ABILITY TO PERCIEVE PAIN • STIMULATION OF THE SENSORY CORTEX EVOKES A SENSATION OF PAIN

  12. PAIN CONTROL (ANALGESIA) • THE ANALGESIA SYSTEM • THE BRAIN’S OPIATE SYSTEM • INHIBITION OF PAIN BY TACTILE STIMULATION • TREATMENT OF PAIN BY ELECTRICAL STIMULATION • REFERED PAIN

  13. THE ANALGESIA SYSTEM • PREAQUEDUCTAL GRAY • RAPHE MAGNUS NUCLEUS • PAIN INHIBITORY COMPLEX IN DORSAL HORNS

  14. PAIN INHIBITORY COMPLEX: PRESYNAPTIC INHIBITION BRAIN STEM.NEURON ANTEROLATERAL PATHWAY INHIBITORY NEURON - PAIN RECEPTOR + DORSAL HORN OF SPINAL CORD

  15. PAIN TRANSMISSION AND INHIBITION • SUBSTANCE P IS THE NEUROTRANSMITTER: BUILDS UP SLOWLY IN THE JUNCTION AND IS SLOWLY DESTROYED • PRESYNAPTIC INHIBITION BY INHIBITORY NEURON BLOCKS THE RELEASE OF SUBSTANCE P (ENKEPHALIN)

  16. THE BRAIN’S OPIATE SYSTEM • OPIATE RECEPTORS EXIST IN MANY CENTERS OF THE BRAIN, ESPECIALLY IN THE ANALGESIA SYSTEM • AMONG THE NATURAL SUBSTANCES WHICH ACTIVATE THESE RECEPTORS ARE: ENDORPHINS, ENKEPHALINS, AND MORPHINE

  17. INHIBITION OF PAIN BY TACTILE STIMULATION • STIMULATION OF LARGE SENSORY FIBERS FOR TACTILE SENSATION INHIBITS PAIN TRANSMISSION FOR SAME REGION • RUBBING OFTEN EASES PAIN • LINAMENTS, OIL OF CLOVE, ETC. • POSSIBLE EXPLANATION FOR ACUPUNCTURE?

  18. TREATMENT OF PAIN BY ELECTRICAL STIMULATION • STIMULATION OF LARGE SENSORY NERVES • ELECTRODES IN SKIN OR SPINAL IMPLANTS • INTRALAMINAR NUCLEUS OF THALAMUS

  19. REFERED PAIN • VISCERAL PAIN FIBERS SYNAPSE ON SAME SECONDARY NEURONS AS RECEIVE PAIN FIBERS FROM SKIN

  20. THE VISUAL SYSTEM D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM

  21. THE VISUAL SYSTEM SENSES ELEECTROMAGNETIC RADIATION • ELECTROMAGNETIC RADIATION (EMR) SPANS THE ELECTROMAGNETIC SPECTRUM (EMS) • FROM RADIO WAVES (VERY LONG) TO -RADIATION (VERY SHORT) • VISIBLE LIGHT IS A SMALL PORTION OF THE SPECTRUM • PHOTONS OF LIGHT INTERACT WITH MATTER

  22. ANATOMICAL ORGANIZATION • THE EYE • CORNEA AND LENS: BEND LIGHT RAYS AND FOCUS THEM ON THE RETINA • CILLIARY MUSCLES LOSSEN OR TIGHTEN TO ADJUST LENS THICKNESS • RETINA: SITE OF PHOTORECEPTORS • FOVEA: MOST SENSITVE PART OF RETINA

  23. SCLERA TEAR DUCT AND DRAINAGE CANAL PUPIL IRIS

  24. EXTERNAL EYE MUSCLE SUSPENSORY LIGAMENT CILIARY BODY CHOROID CONJUNCTIVA RETINA IRIS SCLERA PUPIL FOVEA LENS CORNEA AQUEOUS HUMOR OPTIC NERVE OPTIC DISC VITREOUS HUMOR BLOOD VESSELS STRUCTURE OF THE EYE

  25. THE PHOTORECEPTORS • RODS: CYLLINDRICALLY SHAPED- BROAD RANGE OF WAVELENGTHS, NIGHT • CONES: CONICALLY SHAPED-NARROW WAVELENGTH RANGE, COLOR

  26. BEFORE A PHOTON ARRIVES MEMBRANE POLARIZED NORMALLY AFTER A PHOTON ARRIVES • RHODOPSIN ABSORBS PHOTON AND CHANGES SHAPE • A SEQUENCE OF BIOCHEMICAL STEPS • MEMBRANE HYPERPOLARIZED

  27. PATHWAYS FOR VISUAL INFORMATION • OPTIC NERVE (GANGLION CELLS FROM RETINA) • LEAVES THROUGH “BLIND SPOT” • LATERAL GENICULATE NUCLEUS: PROJECTS TO CORTEX • PRIMARY VISUAL CORTEX

  28. VISUAL ORIENTATION COLUMNS • CELLS IN VARIOUS COLUMNS OF CORTEX RESPOND TO DIFFERENT ORIENTATIONS • THESE DEVELOP DURING THE EARLY VISUAL EXPERIENCES OF YOUNG ANIMALS

  29. COLOR VISION • TRICHROMATIC: RED, BLUE, GREEN • PARVOCELLULAR NEURONS CARRY INFORMATION • DIFFERENT CELL TYPES • COLOR CONTRAST

  30. THREE KINDS OF CONES • RED, BLUE, AND GREEN • CONNECT TO SMALL GANGLION CELLS • TRANSMIT COLOR INFORMATION TO PARVOCELLULAR NEURONS IN LGN

  31. COLOR NEURONS • BROAD BAND: SINGLE COLOR, + INSIDE, - OUT • SINGLE - OPPONENT: EXITED BY ONE COLOR IN CENTER, INHIBITED WHEN ANOTHER COLOR IN PERIPHERY • DOUBLE OPPONENT: OPPOSING COLORS IN BOTH CENTER AND PERIPHERY • ANNULAR FIELDS OVERLAP TO RECTANGULAR IN CORTEX

  32. LENS DEFECTS • FOCUSING IN FRONT OF RETINA • NEARSIGHTEDNESS (MYOPIA) • USUALLY DUE TO WEAK CILIARY MUSCLES • FOCUSING BEHIND THE RETINA • FARSIGHTEDNESS(HYPEROPIA) • LENS TOO STIFF (AGING)

  33. NEARSIGHTEDNESS (MYOPIA) UNCORRECTED CORRECTED

  34. FARSIGHTEDNESS (HYPEROPIA) UNCORRECTED CORRECTED

  35. VISUAL FIELD DEFECTS • OPTIC NERVE:VISUAL FIELD ON SAME SIDE • OPTIC CHIASM:OUTER HALF OF BOTH VISUAL FIELDS • OPTIC TRACT: OPPOSITE HALF IN BOTH VISUAL FIELDS • OPTIC RADIATIONS:LOWER OR UPPER QUADRANT ON OPPOSITE SIDE

  36. THE AUDITORY SYSTEM AND THE CHEMICAL SENSES D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM

  37. THE NATURE OF SOUND • COMPRESSION AND RARIFICATION OF AIR • WAVES OF HIGH AND LOW PRESSURE • TRANSMIT MECHANICAL FORCES

  38. CHARACTERISTICS OF A PRESSURE WAVE A T = WAVELENGTH A = AMPLITUDE f = 1/T FREQUENCY

  39. ANATOMY OF THE EAR • OUTER EAR • MIDDLE EAR • INNER EAR

  40. OUTER EAR • ACTS TO FOCUS SOUND WAVES ON THE TYMPANIC MEMBRANE • SHAPED LIKE A SOUND CONE

  41. OUTER EAR PINNA CANAL

  42. MIDDLE EAR • THREE BONES LINK TYMPANIC MEMBRANE TO OVAL WINDOW • VIBRATIONS TRANSMITTED MECHANICALLY

  43. MIDDLE EAR BONES OF MIDDLE EAR COCHLEAR FLUID SOUND WAVE IN EAR CANAL TYMPANIC MEMBRANE OVAL WINDOW

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